Rice Home |
FA Newsletters
July 9, 1997
In This Issue:
Rice Blast Update
Current Situation
On June 19 and 20, rice scientists found blast in two Glenn Gounty
rice fields (S-201 and M-401) about 4 miles apart. Presence of the blast
fungus, Pyricularia griesa, confirmed the identifications.
Both of these fields had the disease last year. At the present time, the incidence and severity of the disease
appears to be limited and mild, respectively. Observations at other sites
that had blast last year have been negative for the disease.
Typical leaf blast symptoms consisting of diamond shaped lesions
with grey centers and dark brown borders were observed on leaves. A yellow
halo surrounding lesions or yellowing between coalescing lesions were also
observed on some leaves.
Leaf blast is the first phase of the disease and may be followed
by collar and panicle blast. Further development of the disease will depend
largely on environmental conditions.
Blast Information
The University of California has prepared a blast identification
guide and blast fact sheet to show and describe blast symptoms on rice.
The identification guide shows color photographs of the different disease
symptoms and the fact sheet describes and discusses symptoms, disease development,
factors favoring disease and control measures. Both were previously distributed
at the U.C. Cooperative Extension winter rice meetings and through the
California Rice Industry Association newsletter. If you did not receive
them or if you have misplaced them, you can obtain another copy at your
local U.C. Cooperative Extension office.
In addition to this educational literature, we have scheduled
a meeting to show you the disease and discuss more about it (see meeting
schedule attached to this newsletter.)
Disease Control
Water and nitrogen management are important factors affecting blast
disease development. Drought stress, excess nitrogen or nitrate nitrogen
encourage the disease and should be avoided.
Keep fields continuously flooded whenever possible. Drain fields
only when absolutely necessary and only for short periods if you must drain.
Drainage may cause drought stress and causes nitrogen to convert to nitrate,
all of which encourage the disease. Deeper water is less favorable for
the disease than shallow water. Suggested water depths are 4-5 inches
for the early season (up to 65 days) and 8-10 inches for late season (after
65 days).
Avoid the use of excess nitrogen since this enhances disease development.
Use leaf analysis or a chlorophyll meter to check crop nitrogen status.
Topdress nitrogen only if a deficiency exists.
Quadris®, a new fungicide developed by Zeneca Ag. Products,
has been shown to control blast in the southern U.S. and has recently received
a section 18 registration in several southern states. This new fungicide
is not currently available in California, but the California Rice Industry
Association, with the support of the Rice Blast Disease Task Force, is
now seeking an emergency section 18 registration for California rice.
Research Activities
We are working hard to learn more about blast and how to control it.
This spring we established four blast study sites in Glenn County to develop
disease control information. The sites were located in fields that were
known to have blast last year. Each site includes a fungicide trial and
a germplasm selection nursery. One of the sites also includes a rice variety
trial. The Departments of Plant Pathology and Agronomy and Range Science
at U.C. Davis, the Rice Experiment Station at Biggs, and U.C. Cooperative
Extension in Colusa, Glenn, Yolo and Tehama Counties are cooperating on
these studies.
The fungicide trials should provide information on fungicide application
timing and efficiency and the selection nursery should help identify varieties
or experimental lines that could be used to breed for a resistant California
variety. The variety trial may provide information on the relative susceptibility
of our varieties.
Additional studies and efforts are being conducted at U.C. Davis
and at the Rice Experiment Station.
Other
Although we continue to look for blast, we are asking all pest control
advisers and growers to be on the lookout and to let us know if you find
it. If you find blast or if you need further information on the disease,
please call U.C. Cooperative Extension at (916) 458-0578.
Shark® Herbicide Trial Results
With the advent of weed resistance to Londax® and increased phenoxy
drift problems, the development of new herbicides for broadleaf weed control
in rice is extremely important.
In an effort to accelerate the development of Shark® - a new
broadleaf herbicide for rice - area rice farm advisors cooperated with
Extension Rice Agronomist, Jim Hill, to conduct herbicide rate, timing,
and efficacy trials. Three trials were conducted in Colusa, Sutter and
Yuba Counties in l996.
Results from the Colusa County trial are shown in table 1. Shark®,
a new herbicide developed by FMC, showed good control of several important
broadleaf weeds in rice. It provided good control of California arrowhead,
Smallflower umbrellaplant, Red stem, Rice field bulrush and Water plantain.
It did not provide effective control of Ducksalad. Shark® does cause
some bronze leaf spotting on rice, but the crop soon grows out of it.
Since this new herbicide has only been field tested a few years,
we still have a lot to learn about it. The best rate and timing are two
factors that are still under study. FMC hopes to have Shark® registered
for use in California in 1999.
| Table 1. Weed Control Ratings for Shark® Herbicide Colusa County 1996 |
| |
Weed Control2, 3 |
| |
SAGMO |
CYPDI |
AMMCO |
HETLI |
Treat
ment |
Water Depth |
Rate |
Timing1
| 7/18 |
7/18 |
8/22
| 7/18 |
8/22
| 7/18 |
|---|
| 1 |
1-2 inches |
Control |
81 |
0.3 |
0.0 |
0.5 |
0.0 |
0.0 |
0.0 |
| 2 |
1-2 inches |
60 g/ha |
81 |
8.8 |
7.1 |
8.0 |
7.3 |
10.0 |
0.8 |
| 3 |
1-2 inches |
120 g/ha |
81 |
9.2 |
8.0 |
8.5 |
8.3 |
10.0 |
1.0 |
| 4 |
1-2 inches |
180 g/ha |
81 |
9.8 |
8.6 |
8.4 |
8.0 |
10.0 |
1.3 |
| 1 1 = leaf stage |
| 2 SAGMO = arrowhead; CYPDI = smallflower umbrella sedge; AMMCO - red
stem; HETLI = ducksalad. |
| 3 Weed control ratings are from 0-10, with 10=excellent control, and
0=no control. |
Rice Meetings Scheduled
We have scheduled several rice meetings to keep you informed on important
rice production and research topics. All growers, pest control advisers
and other interested persons are invited to attend. The dates, times, locations
and topics for each meeting are described below. For further information,
contact U.C. Farm Advisor Steve Scardaci at (916) 458-0578.
| Rice Blast Meeting |
When: | Thursday, July 17, 1997, 9:30 a.m. |
Where: | Glenn Pheasant Hall, Hwy. 45 about 1.5 miles
south of Glenn, Glenn County |
Topics: | Blast and other rice disease symptoms,
factors affecting blast, disease development, control strategies and current
research. |
| Rice Salinity Field Meeting |
When: | Wednesday, July 23, 1997, 9:30 a.m. |
Where: | Keller Ranch, North of White Rd. and West
of Hwy. 45, Colusa County (Follow signs from White Rd |
Topics: | Effects of salinity on rice, salinity measurement,
highlights of past and current salinity results |
| Rice Field Day |
When: | Wednesday, August 27, 1997, 7:30 a.m. (Registration & Posters); 8:30 a.m. (Program) |
Where: | Rice Experiment Station, Biggs, CA, Hwy
162, 1.5 miles west of Hwy 99E, Butte County |
Topics: | Weed control, variety development, blast
and other rice diseases, rice water weevil. |
Steve Scardaci, UC Farm Advisor,
Colusa, Glenn, Tehama & Yolo Counties
Rice Home |
FA Newsletters
Modified: 10 Sep 1998
Comments to jayoung@ucdavis.edu
Rice Blast Update